The warnings that severe weather is approaching, particularly northwest of Columbus, are
starting to fly this evening.

The Columbus area remains targeted by a massive storm complex with damaging straight-line
winds that could reach 70 mph, the National Weather Service says.

Central Ohio faces two threats from a potentially violent weather system advancing into the
Midwest that was forming late this afternoon in southern Wisconsin.

Isolated thunderstorms are expected to pop up in the heat and humidity this evening ahead of
the most-worrisome storm front, said Myron Padgett, a meteorologist with the National Weather
Service office in Wilmington.

The storms could turn violent, producing large hail and high winds, Padgett said.

Isolated tornadoes are possible, with the worst of the evening weather expected north of the
Columbus area. A flash-flood watch was posted for counties north of Union, Delaware and Licking
counties.

At 5 p.m., the National Weather Service issued a seldom-seen "particularly dangerous situation"
severe-thunderstorm watch for counties north and west of Columbus, including Union, Champaign and
Logan counties, until 2 a.m. Thursday.

The unusual storm-watch represents an enhanced chance of very severe and possibly
life-threatening weather.

The violent storms forming northwest of Ohio will race through the Columbus area with
damaging winds between 11 p.m. and midnight, forecasters said.

“We’re not sure if it’s going to be a derecho or not, but you’re splitting hairs” when winds
could exceed 60 mph, said Jeff Sites, another weather-service meteorologist.

Early this afternoon, the Storm Prediction Center placed northern Illinois, northern Indiana and
a sliver of northwest Ohio at "high" risk for severe weather. The threat in the Columbus area is
rated as "moderate."

A derecho is a widespread, long-lasting windstorm borne by a line of fast-moving thunderstorms
that track across at least 250 miles while spewing out winds in excess of 58 mph.

The Columbus area dreads the “D” word following a derecho with 80 mph winds last year that
wrecked trees and power lines and left more than 300,000 people without electricity in central
Ohio. Some waited more than a week for power to return in the wake of hurricane-force winds.

The June 29 storm left more than 1 million Ohioans without power amid a heat wave in the 90s
and, when coupled with another line of storms that followed the derecho, caused at least $845
million in damage.

Nationally, the derecho interrupted electricity to more than 5 million from the Chicago area
to the mid-Atlantic coast and contributed to 22 deaths. Another 34 deaths followed from the heat
wave baking areas without power.

The gigantic line of powerful thunderstorms could affect one in five Americans today as it
rumbles from Iowa to Maryland packing hail, lightning and tree-toppling winds.

All told, the area the weather service considers to be under heightened risk of dangerous
weather includes 64 million people in 10 states.

“It's a pretty high threat,” said Bill Bunting, operations chief at the National Weather
Service's Storm Prediction Center in Norman, Okla., who also warned that the storms will produce
large hail and dangerous lightning. “We don't want to scare people, but we want them to be aware.”

Today “might be the worst severe weather outbreak for this part of the country for the year,”
said Jeff Masters, meteorology director at Weather Underground.